A. Field of the Invention
This invention relates generally to the fields of telecommunications, and the processes by which telephone calls are switched and routed into a computer system. More particularly, the invention relates to methods for processing telephone calls which originate from remotely located computers or other data terminals (referred to herein as call originators), and which are destined for receipt by a host computer system.
The invention has applications in both commercial and governmental settings. The invention is particularly suitable for use in applications in which the host computer system receives incoming calls from call originators that are equipped with modems that operate according to various different communications protocols. One example would be where the host computer system is the computer system operated at the headquarters of a chain of retail stores, and where the stores are distributed over a wide area. In this example, the call originators could be, for example, credit card swipe machines and electronic cash registers located in the various stores. The methods disclosed herein are performed by an element of communications equipment we have called a "network access server", which is connected to the host computer system via a network. The network access server receives the incoming calls and routes them to the host computer system in an efficient manner using the techniques of our invention.
B. Description of Related Art
Computers and other terminals that generate digital data presently have the ability to transfer files of information to a remote host computer over the public telephone network. The device that permits this function to be performed is a modem, one of which is placed at the remote data terminal and another of which is placed at the host computer. A modem is a device that modulates the digital data onto to an analog telephone line at the remote location and demodulates the data from the telephone like at the host computer, extracting the digital data.
For an individual or business that owns a single computer, a single modem will ordinarily be all the equipment that the individual or business needs to interface the computer with remote computers to receive incoming data communications. For most business and governmental institutions, however, much more is required in terms of communications equipment. Large businesses, such as the national retail chain referred to previously, may typically have to have the capability of both receiving perhaps hundreds of incoming calls at any one time originating from remote computers or data terminals, and also routing those calls to various different computers arranged in a local or wide area network. Obviously, much more sophisticated communications equipment is required for such large scale operations.
A problem that arises in such large scale operations is that the calls are incoming from a wide variety of types of data terminals, and the modems connected to the data terminals may operate according to a wide variety of different communications protocols. Referring again to our example of the large business, the call originators may include a credit card swipe terminal and its associated modem, electronic cash registers which are also linked to a modem, and perhaps a network of computers located in regional offices that are linked by modems to the telephone system which are used for periodically forwarding sales or inventory reports to the headquarters. Among this set of call originators, the credit card swipe terminals may communicate according to the 300, 1200 and 2400 baud V.22 bis asynchronous protocols. The cash registers may communicate according to the Bell 208B 4800 baud half duplex synchronous or V.32 bis protocol. The computers at the regional offices may also use different communications protocols. In order for a prior art network access server to handle these various communications protocols, it has to go through time-consuming handshaking routines at the start of each call to determine which communications protocol is being used by the call originator, and then configure the modem accordingly. When the costs of computer access time and long distance call time are considered, this extra cost becomes a burden on the profitability of the business. If the business processes millions of calls per year, these costs can become very significant.
In recent years, the trend in telecommunications has been to design equipment that decreases the call connection and transmission time, with a goal being to reduce costs. One change that has been implemented is the installation of digital telephone communications lines, such as the so-called T1 digital system. This system is a 24-voice channel, 1.544 Mb/s, time division multiplexed carrier system. General background information on this system is located in the Electronic Engineers' Handbook, ch. 22 (3rd Edition, 1989), which is incorporated by reference herein. This system permits rapid transmission rates and the stacking of multiple data channels into a single trunk. The T1 system, and other digital systems such as the ISDN system, are preferred data transmission modes by entities which handle a large volume of incoming calls from data terminals, principally because of the high data transmission rate.
One feature which is available with T1 digital telephone service is that the telephone company has the capability of placing control signals onto the telephone line at the beginning of the call. These control signals, which at the present time are typically in the form of multifrequency tones (discussed in detail below), are presently used to identify the carrier access code, which is the number dialed by the call originator. This service is presently known as Feature Group B service. An additional telephone company service, known as Feature Group D, imparts other control signals, again in the form of multifrequency tones, that are identified with the telephone number assigned to the call originator. The technique is similar to the concept of "caller id." Besides multifrequency tones, other types of control signals can be imparted onto the telephone line, such as ISDN and out-of-band signalling techniques. Techniques are becoming available whereby a remote computer user may input control signals directly into the telephone line.
The present invention describes techniques for making novel and advantageous use of these control signals to further reduce the transaction processing and communication time, and/or to permit the network access server to make customized use of these signals. Briefly, in an important aspect of the invention, the invention makes use of the control signals by correlating the control signals to different communications protocols used by the various call originators. The control signals are used to configure the network access server prior to the completion of the call connect process, resulting in significantly reduced communication connection and processing times. The invention further permits the host computer system to process and make use of the control signal in parallel while the call setup and modem configuration process is being performed. In another aspect of the invention, the network access server extracts the control signals and uses the control signals to run specific applications programs (e.g., to do data base look-ups, to set up specific menu screens) or other activities on a customized basis, all based on the extracted control signal. The invention is also capable of performing customized routing of the incoming calls based on the control signals extracted from the incoming call.
Another example of prior art techniques to speed transaction time in credit card processing is the use of high speed asymmetrical communications technologies. An advanced version of this technique, invented by Dale Walsh and Clifford Wallach, is explained in their U.S. Pat. No. 4,890,316, which is assigned to U.S. Robotics, Inc., the assignee of the present invention. Briefly, this technique involves the recognition that during the first part of a credit card transaction call when the request is being sent, the modem for a call originator credit card terminal sends a relatively large amount of information to the called modem at the host computer system during the credit card transaction call. During this part of the call, only a small amount of information is sent the other way. When the acknowledgement is sent from the host computer system to the credit card modem, the remote credit card modem has very little information to transmit, while the modem at the host computer has a relatively large amount of information to transmit. In the invention of the '316 patent, the credit card modem transmits the credit card request at a very high data rate, while the host modem simultaneously transmits information in the opposite direction at a very low rate. After the credit card request is transmitted, the transmission rates reverse so that the host computer modem transmits at a very high rate, and the credit card modem transmits at a lower rate. This asymmetrical mode of communication can substantially reduce credit card transaction time. The present invention takes advantage of this prior art technique in a new and unexpected way in an integrated network access server.
Yet another way the prior art has attempted to speed up the communications process is to develop advanced modulation schemes, data compression techniques, and to use faster data transmission rates, which permit larger blocks of data to be transferred per second to the host computer system. The present invention provides improved call processing techniques that permit a network access server to adapt to such advanced modulation techniques, and to adapt to new modulation schemes that are developed in the future, thereby taking advantage of improvements in the art as they are made.
Because the invention is applicable to a variety of call originator equipment and to a variety of host computer systems, some of the terms used herein are given generic meanings. For example, the term "network" refers to the data transmission element that routes the incoming communications from the network access server to the host computer system. A local area network such as a Token ring local area network is just one example of a "network." An RS 232 serial port which couples the network access server to a stand alone computer is also considered to be a separate example of "network." Similarly, the term "host computer system" as used herein is used generically to refer to the computers that are connected to the network, whether they be a mixture of mainframe computers, a group of personal computers, or even a single computer. Similarly, the term "call originator" is a generic term referring to any data terminal which is connected to a telephone line and which calls into the host computer system. Examples of call originators are an electronic cash register, a credit card swipe, a lottery ticket machine located in a convenience store, and a computer terminal. The term "network access server" refers to the communications equipment that contains a modem and interfaces between the incoming telephone lines and the network.